?9 desaturase (?9D) introduces a cis double bond at the 9, 10 position of stearoyl-ACP to form olelyl-ACP. Preliminary spectroscopic studies indicate the enzyme contains a novel oxo- or hydroxo-bridged diiron clusters. 1H NMR shall be used to characterize the paramagnetically shifted resonances associated with the oxidized and reduced iron centers. Further, the temperature dependance of the chemical shifts will be examined to determine if the ferrous ions are anti-ferromagnetically coupled.